Is there a need to reply to "Thank you" emails ?

Hi

As per my view point Thank You emails should be answered where the client is of supreme nature to your concern and in turn it add to your personal behaviour and you gain a extra edge in the eye of others which delibaretly inculcates a respect for you and moreover increase the goodwill of the company you represent.

Yes. It may not be necessary to Reply to All while a lot of others are copied in but  yes, first and foremost saying Thank You to the person sending it means that you received the email. Saying thank you is by way of connecting to other people. It is important to understand that the reply Thank You may not be so much counted in your busy world and overloaded inbox but the lack of response means you did not acknowledge the person for the action or intent. Behind every message is a person and what counts is that you connect.